Tim Vandergrift

Many people, when asked what a hydrometer does, will answer, 'Measures alcohol'. Some will say, 'Measures sugar'. Neither answer is true. Hydrometers compare the the ratio of the density of the liquid to the density of water, and that's all. It's what we can do with this reading that's useful to us. 

If we use a standard home winemaking hydrometer on our must before fermentation, the liquid will be very high in sugar, and thus will have a density higher than that of pure water. Depending on the wine type, it could by anywhere from 1.070 to 1.110 times as dense. After we pitch yeast and the fermentation is ongoing, the sugar will be metabolised into carbon dioxide and alcohol. As the sugar levels drop, the density of the must will go down and the hydrometer won't float quite as high. This drop shows us the progress of fermentation--which is why it's important to record the initial gravity reading, so you can compare it. More on this below. 

As fermentation completes, all of the sugar is gone. It's normal to assume that the hydrometer would now read 1.000--without any sugar it should be only as dense as water. But that's not the case: alcohol is far less dense than water and since your wine is now somewhere between 10% and 16% alcohol, it's going to read lower--usually between 0.990 to 0.998.

In addition to demonstrating the point at which fermentation is complete, we can use the reading we initially recorded (told you there'd be more) and our final reading, along with a bit of math, to determine the alcohol content of the wine. You take the difference between the two readings and multiply it by 131. Don't worry about the 131--it's a derived number, just remember it.

For example, if your gravity started at 1.090 and the wine finished at 0.994, the difference between the two numbers is 0.096. Multiply 131 x 0.096 = 12.576, or about 12.6% Alcohol by volume. Pretty neat, no? There's a little chart, provided with each hydrometer, for applying temperature corrections (warmer liquids are less dense than cold ones) but for most purposes your wine will be the same temperature each time you measure it. What could be more accurate?

I've written about wine decanting and aeration in this space before, but I recently came across a very interesting take on pouring from an unlikely source: the porrón. 

It would certainly reduce over-consumption, because I'd never hit my mouth

Photo courtesy Wikimedia Commons

As stated by Wikipedia, A Porrón is a traditional glass wine pitcher, typical of Catalonia but famous throughout Spain. It resembles a cross between a wine bottle and a watering can. The top of the bottle is narrow and can be sealed off with a cork. Stemming upwards from the bottom of the pitcher is a spout that gradually tapers off to a small opening. Seems cool enough, and a cheerfully playful sort of decanter. It's design, however tries to minimise contact with air, and makes for pretty slow (if long-distance-capable) pouring

There are some moments, in the making of a wine kit, when you could find yourself reconsidering what you're doing and wishing you hadn't started. Okay, that may be an exaggeration, but you might want to lift a few weights or get your arms and lower back in shape before starting your first kit. Because you're going to be doing quite a bit of stirring, and this doesn't mean a slow, dreamy figure eight through the liquid a couple of times. Before you're done, you'll have to stir till your teeth rattle.

The first thing you do with your kit is make it up to 6 gallons or 23 litres of total volume. But concentrates are very viscous, so unless you stir so them thoroughly into the water, they'll tend to sink to the bottom. You'll have a less dense layer of water infused by a thin gruel of concentrate sitting on top, with the thick, gooey majority of the concentrate lurking like mud below. If these layers are left like this, you'll get a weak fermentation on top, and none at all beneath, resulting in a low-alcohol, high-sugar, thin-tasting wine.

Mmm, pie

Remember your aunt or your friend's grandmother, who could make a perfect cake or dinner dish without ever following a recipe? In making wine kits, of course that is NOT how you should approach things. Kit instructions are very important, and every small step is there to make sure the wine turns out beautifully. But those great cooks and their pioneer predecessors can still be a smart object lesson for us home winemakers. They weren't born knowing their recipes, after all, but learned by trial and error until they discovered what worked.

And after all those trials, how did they remember whether the cake worked better with a half cup of sugar or a quarter cup? They wrote it down. Many of these early settlers used notebooks for keeping track of experiments they made with each meal, recording what the results were. If something went wrong, they'd know for sure what not to do again. And if something turned out very well, they could reproduce the same result next time or tweak it to taste even better.

That's why, as home winemakers, we need to write everything down. Sometimes if a process doesn't occur when it's supposed to, or something takes a lot longer to finish than it should, we can go back to our notebooks and trace where the problem likely started. I might think, “Okay, I shouldn't keep the wine at the lower end of the temperature scale next time.” Or perhaps you'll discover, “The specific gravity hadn't quite reached the needed level, and I started the next step too soon.”

Staphylococcus biofilm. Image courtesy Wikimedia Commons

Cleanliness is next to goodliness in home winemaking. I’m not sure who said this, but the crashing bore was completely correct: nothing can spoil a batch faster than bacteria or wild yeast living on the remains of a previous effort. That’s why winemakers are always vigilant with rinsing bottles after they’re empty, and slosh sulphite around their equipment with great abandon. Keep your equipment and bottles free of debris and treated with a bacterial suppressor like sulphite solution and it will always be ready to go, right?

Sadly, not always—in fact this regimen can leave your equipment a cause of failure, rather than a source of success. Simple rinsing may remove visible residues from surfaces, but after repeated exposures to batch after batch of wine even the ultra-smooth surfaces of glass carboys will develop an invisible layer of colloids and proteins, sometimes described as a bio-film.

This film is analogous to the film that develops on your teeth. And, just as in keeping carboys clean, if you only rinsed your mouth after eating, and perhaps took a swish of mouthwash, you would, in a very short period, find yourself with a serious oral hygiene issue.

Even soaking equipment in quite powerful oxidising cleansers (chlorine-based powders, peroxides or bleach) or powerful reductive agents (sodium hydroxide/caustic soda) won’t completely remove biofilms. This requires the mechanical action of scrubbing to remove the film. Again, we can go back to teeth: even if you rinsed with very strong mouthwash, you still need the mechanical action of brushing to remove the debris from tooth surfaces to be kissing fresh.

One of the ways I’ve illustrated this in the past is a demonstration I did with a very high-volume consumer winemaker. He had made hundreds of batches of wine over a period of a couple of years (big extended family, thirsty friends, lots of parties—he was very popular!) He was methodical, thorough and meticulously clean, but he had thought that a few minutes soaking with cleansers and sulphite treatment was enough. I got him to use a very specific cleaner, Diversol BX/A, a pink powder sold under a variety of trade names. It’s a very powerful oxidising cleaner that also contains detergents, surfactants and potassium permanganate. At my direction he soaked all of his carboys in a strong solution for 20 minutes, scrubbed them with a brush and left them overnight. In the morning when he saw the layer of muck—it looked like sticky brown algae—in the bottom of his carboys, he was convinced of the power of scrubbing, if not a little queasy.